The present invention relates generally to storage batteries and, more particularly, to a method for creating an interface which prevents cell to cell discharge in batteries employing intercellular plate straps electrically connected to battery plate lugs.
Lead acid batteries provide a common source of power for many applications. It is known and desirable to reduce the mass of the battery, the height of the battery, and the number of electrical connections in the battery by casting battery plate straps to battery plate lugs as a solid rectangular piece of lead. This piece of lead not only fuses identically polarized plates within a battery cell but also connects two adjacent cells thereby providing a series connection.
Typically, this arrangement is created by first casting the battery plate straps to the battery lugs in a single cell while the cell is located outside the battery case. Adjacent cells are then placed within the battery case and an intercell weld or bond is formed through or over the partition which separates the adjacent battery cells.
Partitions are necessary in batteries such as the lead acid battery to prevent intercell mixing of acid. Although this problem is limited in an AGM lead acid battery, partitions are still necessary to prevent intercell gas communication. This phenomenon can decrease power output and the life of the battery.
Although the above-described arrangement achieves the above referenced advantages, the arrangement has deficiencies because the intercellular connection of the lead plate strap renders a gas restrictive interface very difficult. The top surface of the battery plate strap is well defined by the mold and its location in reference to the elements within each battery cell can be controlled by a casting machine. However, the battery straps often do not have uniform thickness and the bottom surfaces of the straps are typically rough. These two conditions compounded renders any gas restrictive interface between the plate strap and the battery case partition almost impossible. The additions of sealants or fillers have not proven entirely effective in curing this problem and are of limited application.
It is thus desirable to provide a method of creating a gas restrictive interface between the battery plate straps and the intercell partitions in order to achieve the advantages of the above described arrangement while maximizing battery power and life.
This invention offers advantages and alternatives over the prior art by providing a method of creating a plastic to lead interface which prevents communication of any substance between adjacent battery cells at the point that the battery plate strap extends through the case partition. The battery plate strap must extend through the case partition to permit a series connection of the battery cells. The present invention provides a gas restrictive interface at this partitionxe2x80x94plate strap conjunction which prevents intercellular communication of substances thereby maximizing battery power and life.
The method includes preparing a battery element case having at least one partition with a notch of horizontal and vertical length substantially equal to the width and height of the corresponding battery plate strap. The notch is substantially covered with a reduced plastic. The battery elements are partially inserted within the battery element case and the battery plate straps are cast to the battery plate lugs and between the battery cells. The elements, while still warm, are then fully inserted within the battery element case which causes the battery plate strap to come into contact with the horizontal and vertical portions of the reduced plastic covering the corresponding notch. Due to the heat of the battery plate strap, the reduced plastic surrounding the three sides of the battery plate strap melts or softens and thereby surrounds the battery plate strap and creates a gas restrictive interface.
The fourth interface is created on the top of the battery plate strap after placing the battery case lid onto the battery element case. The lid has a plurality of complimentary notches which each correspond to an individual case partition. The horizontal portion of the complimentary notch has a length substantially equal to the width of the corresponding battery plate strap and is covered in a reduced plastic. As the lid is placed onto the battery element case, the reduced plastic of the complimentary notch comes into contact with the top of the battery plate strap. The heat from the battery plate strap causes the reduced plastic of the complimentary notch to melt or soften and form a gas restrictive interface with the top of the battery plate strap. At this point, a gas restrictive interface has been effectively created between the battery plate strap and the case partition.